Old Bulbs = Algae

[Myka]

The reason for the algae growth is because most bulbs will actually have a fairly significant spectrum change. The spectrum goes red, yellow, white, blue. Not sure what red is (0K?), but yellow is 5000K, white is 10,000K, and blue is 20,000K. Everything in between is in between (go figure!). Whatever color it starts as (blue or white) it will fade towards the red spectrum. A new bulb being 20,000K may be 16,000K after a year. A new bulb being 10,000K may fade to 7,000K. Each bulb will fade a bit more or a bit less than the next bulb, and the ballast will also influence. The red spectrum encourages plant growth, that is why horticulture bulbs are low Kelvin like 5500-6500K.

[randallino]

What effect does age have on T5 fluorescents?

[Myka]

Same thing, but quicker. It's the same for all bulbs, including household bulbs. To avoid this spectrum fade it is wise to change bulbs at certain times according to the type of bulb:

Halides 12 months
T5HO 8 months
Compact Fluorescent 6 months
VHO 12 months

Over-driving the bulbs will cause them to fade faster, like say using a mogul halide bulb on an HQI ballast. Using fans on the bulbs to keep them as cool as possible will help them perform better in their usable life as well.

[chris88]

The spectrum and intensity does change in various lighting bulbs but its not the major causes of an algae bloom. Algae will grow because there is an access of nutrients. You could put a ton of red over a tank will low nutrients and no algae will grow. In fact that’s what people are doing with the new fiji purple and ati purple plus bulbs, they are adding red spectrum. If you have excess algae growth you will have access nutrients (nitrates, phosphates, silica, etc). However, the added red and yellow spectrum will make a high nutrient tank grow algae much faster because algae use red spectrum very well for photosynthesis.

[daniella3d]

In deed. I have a fugi purple that is very red on my other tank and no algae grow. I used to have PC that were near a year old and no algae either.

I use GFO in both my aquarium + micro algae and not overcrawding and that does the trick.

We must not forget that zooxanthellae are algae and that coral need them to grown, at least for photosynthetic coral.

Originally Posted by chris88

The spectrum and intensity does change in various lighting bulbs but its not the major causes of an algae bloom. Algae will grow because there is an access of nutrients. You could put a ton of red over a tank will low nutrients and no algae will grow. In fact that’s what people are doing with the new fiji purple and ati purple plus bulbs, they are adding red spectrum. If you have excess algae growth you will have access nutrients (nitrates, phosphates, silica, etc). However, the added red and yellow spectrum will make a high nutrient tank grow algae much faster because algae use red spectrum very well for photosynthesis.